An α-sulfonated fatty acid ester salt (α-SF salt) is conventionally distributed in the form of a solid product (such as a flake or a powder), and is mainly used as a washing component of a powdery detergent. However, in the case of using an α-SF salt in a liquid detergent, it is necessary to preliminarily prepare a liquid obtained by dissolving or dispersing a flaky solid product of an α-SF salt in water, etc. before an α-SF salt is added into a main mixing chamber.
In addition to an α-SF salt, a linear alkylbenzene sulfonates (LAS) and a polyoxyethylene alkyl ether sulfate (AES), etc. are widely used as a washing component of a detergent. These LAS and AES have already distributed in the form of a high-concentration solution (a condensed solution).
The viscosity of an α-SF solution generally increases as the concentration thereof increases. When the concentration reaches about 30 wt % or more, an α-SF salt forms a hexagonal structure and becomes in a gel state which has lost fluidity. When a gelled salt is heated under normal pressure so as to evaporate the water thereof and to condense the gelled salt, the viscosity decreases under a heating condition of 50° C. to 100° C., and a gelled salt becomes in a slightly flowable state within a certain concentration range. When further continuing this condensation, the viscosity increases again, and the fluidity is lost. Under this kind of a fluidity-losing condition, the transportation by a tanker or a ship is difficult, and transportation costs, etc. are required.
In contrast, there has been proposed a method of improving the fluidity of concentrated α-SF solution.
For example, there has been disclosed the method of using both of an α-SF salt at a specific amount and an alcohol having a carbon number of 6 to 22 in which the proportion of a branched alcohol is 60 mass % or more (see Patent Literature 1). According to this method, a fluidity-improving effect is obtained at room temperature (about 25° C. to 30° C.).